It comes out your nose when you sneeze, on droplets of snot, or when you blow your nose. They scrape your sinuses (which are very far up past your nose) because the sinuses are what produce the snot (mucus). Your nose itself does not produce the mucus, it's just skin and hair in there.
They could probably have you blow your nose or force you to sneeze to collect the mucus, but it would put the doctor and anyone else in the room at risk. It's much safer to have the mucus directly on a cotton swab, as the cotton holds the fluid on it quite well. Cotton is a very absorbent material, hence why it's used for wicking (kerosene heater wicks, ecigarette wicks, oil lamps, candles, etc)
If COVID is falling out of my nose why do you need to scrape my brain to test for it?
It comes out your nose when you sneeze, on droplets of snot, or when you blow your nose. They scrape your sinuses (which are very far up past your nose) because the sinuses are what produce the snot (mucus). Your nose itself does not produce the mucus, it's just skin and hair in there.
They could probably have you blow your nose or force you to sneeze to collect the mucus, but it would put the doctor and anyone else in the room at risk. It's much safer to have the mucus directly on a cotton swab, as the cotton holds the fluid on it quite well. Cotton is a very absorbent material, hence why it's used for wicking (kerosene heater wicks, ecigarette wicks, oil lamps, candles, etc)